Heat of Fusion


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heat of fusion

[′hēt əv ′fyü·zhən]
(thermodynamics)
The increase in enthalpy accompanying the conversion of 1 mole, or a unit mass, of a solid to a liquid at its melting point at constant pressure and temperature. Also known as latent heat of fusion.

Heat of Fusion

 

(or latent heat of fusion), the amount of heat that must be supplied to a substance in an equilibrium constant-pressure and constant-temperature process to convert the substance from the solid (crystalline) state to the liquid state. The same amount of heat is liberated when the substance crystallizes.

The heat of fusion is a special case of the heat of a first-order transition. For a given substance, the heat of fusion may be determined per unit mass or per mole. In the former case, the heat of fusion is measured in, for example, joules per kg (J/kg) or kilocalories

Table 1. Heat of fusion of several substances
Substancetm(°C)Lf(kcal/kg)Lf(J/kg)
Hydrogen ...............–259.113.8958,200
Nitrogen ...............–209.866.0925,500
Mercury ...............–38.892.8211,800
Ice ...............079.4333,000
Tin ...............231.914.460,300
Lead ...............327.45.8924,700
Copper ...............108348.9205,000
Iron ...............153965272,000

per kg (kcal/kg). In the latter case, the heat of fusion may be expressed in joules per mole. The term “molar heat of fusion” is sometimes applied to the heat of fusion per mole. Table 1 gives the values of the heat of fusion per kg Lf for several substances at atmospheric pressure (760 mm Hg, or 101,325 newtons per m2) and at the melting point tm.

References in periodicals archive ?
6, and both the melting temperature and heat of fusion of the pCBT resins are summarized in Table 2 with respect to annealing time.
6[degrees]C, ~42[degrees]F), high heat of fusion (~200kJ/kg, ~86 BTU/[lb.
These results made lauric acid an extremely interesting candidate PCM for this project based on its melting temperature range, high heat of fusion and minimal supercooling, and inherent safety for human health and the environment (listed only as a mild irritant (Alfa Aesar, 2009); the material properties are displayed in the Table 2 below.
It was also found (Table 1) that the heat of fusion of PVDF in the composite decreases with BT content.
Ignoring the heat of fusion can introduce serious errors when processing polymers like HDPE or nylon, where it can account for a major portion of the total power for heating and melting the resin.
The decrease in the heat of fusion can be explained on the basis of reduction of crystallinity due to disruption of crystallizable sequences upon addition of defects (ethylene units).
This coincided with trends in the heat of fusion of PET in the DSC thermograms shown in Fig.
The maximum heat of fusion obtained in the films was directly proportional to the crystallization temperature; larger heats of fusion occurred in films crystallized at higher temperatures.
Heat of fusion of PEN moiety for alloy sheets was calculated by the following Eq.
When the liquidus temperature is reached and austenite is precipitated, heat of fusion starts evolving and increases further when the eutectic temperature is reached.